Prerequisites and gates
If a topic needs something you have not done yet, Wobo says so and offers to cover it first. You can always go ahead anyway.
A gate in Wobo is advice, never a wall. There is no locked padlock and no "complete the previous unit to continue".
What you see
One quiet line before you start: what this topic leans on, whether you have it, and a shortcut to the missing piece. Then two doors: cover that first, or carry on.
Where the advice comes from
Every topic is joined to the ideas it depends on. Wobo knows which of those you can do on your own, which you can do with help, and which you have not met. The line you see is built from that, not from whether you clicked through a unit.
The bridge
If you do go ahead, Wobo teaches the new thing using only ideas you have actually mastered as the stepping stones. Same destination, different route, built for what you personally know. That is often better than going back.
If you joined mid-school
Wobo will not send you two years back because a graph exists. Gates are scoped to where you started.
Turning the advice down
Choose "carry on" and Wobo drops it for that topic. Wobo does not ask twice.
Related: Your progress.